Benefits of Aggregate Surfacing
  1. Protection from foot traffic of other trades during construction and afterward for routine roof maintenance.
  2. Weight as additional protection for wind uplift.
  3. Reduced surface temperature.
  4. Even flow of water to the drains.
  5. Fire protection from burning brands. .
  6. Protection of bitumen from the ultraviolet rays of the sun and effects of hail.
  7. Most important - by using an aggregate surface, an additional minimum average of 70lb/square (31.8kg/9.3m2) of coal tar or a minimum average of 55lb/square (24.9kg/9.3m2) of asphalt (asphalt specifications only) is included in the installation.
The aggregate surfacing must be applied into the top pouring while the bitumen is still hot so that a continuous layer will be adhered. The completed roof assembly will have a continuous aggregate surface. Depending on gradation of aggregate, weights may vary. Occasionally, on well applied roofs, small black globes known as "raspberries" or "blackberries" will form in the roof surface. These are not detrimental to the roof. Reference: Surfacing Time.

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